Light meter



Patented Mar. 13, 1945v 'rheinvention here disciosedrelatesto light meters, for photographic or lfor any' other light measuring purposes.

AObjects of the inventioni'a-re# to provide an "disc `afi-lat" planea's* 'shown in Fig.'` 4. This provides a narrow rim portionA I9, of continuously varying thickness Ito `match the constant thick- -ness 'of' the standard-light measuring member: 7.

accurate reliable formo'f light meter, which will y5 `Stop pins -20, 2I,arelindicated in Figs. 3 andv4,

not require any"e1ectric dry cells andthe like.

*light and the fneedf-Lfor Other important objects are to @provide-afs'im 22; inthe back of thedisc, to limit the extent ple, inexpensive form of `device,"sr'nal1'enough'fto be kept in a pocket or carriedin the hand', which will have no parts to wear `out -andfwhichfwll -be'ready fcrinstantuse always. f

Other desirable yobjects and the novel features of the invention by which'all objects/arcati tainedv arehereinafter set forth for will appear in the course ofthe followingspecification. l

The drawing accompanying andf'formingfpart of the specificationv illustratesa present practical 'embodiment of the invention. Structure"howl evermay be modified' alnd changed au with-inthe i 'true intent and broad 1.scope of the `in`vention vas hereinafter deiinedandclaimediU- Fig. 1 in the drawing is a front elevation of the device.- v 'f Fig. 2 is a side view of the same.

Fig. 3 is a rear view.

Fig 4 is a horizontal sectional view. on substantially the plane of line 4 -4 of Fig. 2.

The base of the device is shown as consisting' engaging in a less thancomplete circular groove oifrotary adjustment and to 4assist the vusers-in s'ettir'igk the `deviceto an initial position. either for the maximumor theflminimum light 'y in# tensity.1= l Y TO'feXClude Sidelight and aid the user in quick;

lyv reaching accurate 'and` ne adjustme'nta'a viewingtube is shown yat 23,- pivoted on the back offfthe panelby means of pins' 24, entered in slots springs'iiZ'Ifwhich hold the tube either vabutted flrmljagainstthe panel, Iover the4 viewing openingierj-foidednatdown overige back of the'panei forminga protective covervv for the opening".

When"'foldeddow`n as in the dotted lineslFig. 2, the -tube lies fiat against the back panel, taking f up i but* v"small space .and *closing the lv'opening against" the 'entrance of `dust or' other 4:foreign matter. v

variable density light' disc one way or the other until that point is reachedwhere the light ,ap-k pears to be of equal intensity in the two halves l of the viewing opening.

The adjustable disc is shown as carrying a scale` or'graduations 28, registering with a pointer 29,-

' providing a measure which can be taken'oi on a suitable materials and they are shown in the general form of discs, one small and the other larger, set in circular seats 9, I0, inthe face ofv the panel.

The smaller member 1, is shown arcuately notched at Il, to t the periphery of the larger disc 8, and as held loosely centered on a stud screw I2, and yieldingly pressed against the edge of the larger disc by a pin I3, engagedk by spring I4.

Disc 8, is shown rotatably centered on a stud screw I5, and as having its edge milled or knurled at I6, and exposed through a notch II, in the edge of the panel.

The variable density effect isattained byv making the rim portion of the comparing disc as a circular helical plane I8, with the back of the -rotary scale 30, co-operatively relatedl to a iixed scale 3|, which may carry desired -readings such as for certain photographic stops, times of exposure and the like.

`The helical inclined plane forms a continuously variable wedge of light permeable material.'r instantly adjustable to any angular extent to match the light intensity of the xed light transmitting member. The yielding edge-to-edge engagement of the two members prevents any perceptible light crevice between these members` and enablesv the non-rotating member`to yieldingly retain the rotatable member in any positions of adjustment. The spring I4 which through thef asuste mounted ln edge-to-edge relation over said light passage, one of said elements being rotatable and the other non-rotatably mounted and the latter having a notched edge rotatably receiving the edge portion of the rotatable element, the rim portion of said rotatable element being in the form of a flat helix increasing in thickness from one end to the other.

5. A light meter, comprising a support having a light passage-.light transmitting elements mountelements mounted on said panel in edge-to-edgel relation over said light passage, one of saidlz'i' ments having that portion of the samer-over -s'aid ed in' eagitoaed'ge relationiover said iight passage, one of said elements being' rotatable and the other non-rotatably mounted and the latter "having a notched edge rotatably receiving the 'dge'portion of the rotatable element, the rim portion of said rotatable element being in the passage of continuously varying thicknesl "'Toimo 'ai'it helix increasing in thickness from mounted for movement on thp'anel to'fbrlgpoi i tions of diierent thickness into coactive relation lione-enti to `tl1e`^"otlier, the edge of said rotatable elementprojecting from the edge of the support with said 'other element and the portion "of *sijo foiifo'ilitating rotary adjustments of the same.

otherV "element over said light passage being-f bf substantially uniform tiriiclmess.k

g2'. 'A flight meter; comprising-al pai-rel-havingfaJ lightfpassage therethrough, light-A utransmitting 1 Ipassagegone-foisaidfn'ieiribersV sbeingV rotatably elements `mounted Von .said .panel in 'iedge-to-edge engagement over vsa-id light passage, -onefof --said elementsf'having .that portion off-the same 'over said Vpassage -of continuously i `varying thickness,

`mounted for.movement on the panel to bring fportionsof different thickness-intoy coaetive relation with said other element and means for tensioning said elements into*frictionalredge-to-edgeholding engagement lwithv eachother. l y

3; A 'light meter,A comprising ia supportflhaving a .flight passage, Ydisc4 members of -lightftransmitting. rnaterialA mounted on sai-d support,Av one in rotatable andthe 'otherinnen-rotatable; edge-t0- edge,L relation over said `lig-ht passage;v :said-119,11; rotatable elementV` having its edge notched tol viit 4the edge of ythe yrotatable element IandA thellatter bad/ing the rim 4portion of the `same varying -iheknQsS-f 1 4.Af light 'meterg comprising a supporthaving a L light f passage, vmlight transmitting elements A-lightmeteracomprising a panelfhaving a alight l:passage atlfierethrofugh,-` alight :transmitting members mounted on the iaceof..the.panel;-in abutting -edgeeto-edge relationship over-said light mounted on said panel and Yhaving a ycircularly extending portion of varying thickness and-light ,tr:imsmisrsibi-lity,-v saidmember :having an` exposed 'finger' engageable .portion for turning lthe v same and-moaned@ limitingffthe extentpf turningadnstment of Isaid-nriemhert- 7. A light meter,comprising-Jarsupport'having -a -;liglit message, flight-. transmitting members mountedsinnedge-fto-edge'relationon said support overfsaid.lightpassageeone oi-said-members-hav- 40 ,andy@deems iorfyieldingly. pressing-said notched member against- 'the edge of the lrotatable member to yieldlngly hold nthe latten in .adjusted relation.

soenna fr. 

